JDemo is the Java demonstration framework. Its concept is similar to the one of JUnit.
As supplement to test driven software development, JDemo provides a new approach of demo driven development: When developing software you write short code snippets (demo cases) that use your new API. The demo then demonstates both: how to use the API and what happens when you execute the code. So you can interactively test the usability of GUI components, for example.
JDemo has a lot of convencience classes and methods that make implementing those demos very easy. The demos can then be launched from a Swing application called Demo Runner.
Demos can also be used for automatically taking screenshots for documentation purposes.